The benzodiazepines have found wide therapeutic use in the treatment of anxiety and other clinical disorders. While neuronal benzodiazepine receptors have been described, much remains to be learned concerning this receptor and its mechanism of action. To study the benzodiazepine receptor, cDNAs that direct its expression have been identified. In this proposal, the characteristics and expression of a cloned cDNA and its use in understanding benzodiazepine receptor structure and function will be explored. Initial experiments will be aimed at ensuring that the cDNA encodes a central benzodiazepine receptor. The binding properties and size of the protein expressed in transfected cells will be compared with those of the benzodiazepine receptor in brain membranes. In addition, the tissue distribution of mRNAs complementary to the cDNA will be determined by Northern blot analysis and in situ hybridization histochemistry. This will establish that the mRNA is present in appropriate brain regions. Once the identity of the cDNA has been established, it will be characterized in detail. By analyzing its DNA sequence, the complete amino acid sequence of the receptor protein will be determined. This information will provide a basis from which to examine receptor structure and function. Further studies using Southern and Northern blot analysis will determine the number of genes and mRNAs directing receptor biosynthesis. These studies will provide insight into the basis of receptor heterogeneity in the central nervous system and probe the relationship between central and peripheral receptor types. In this proposal, cellular and molecular biological approaches will be used to characterize the benzodiazepine receptor. These studies will enhance our understanding of drugs of great clinical importance.